High resolution timers?

Started by arhodes19044 April 1, 2005

Is there an external timer commercially available and relatively
inexpensive that is easy to interface to a BX-24?

I am hoping to find something accurate to a few seconds a year and
with better granularity than 1/512 of a second. Temperature
compensation would be a great thing as well. Lithium watch battery
backup would be great too!

Any ideas of what to use?

-Tony




--- In basicx@basi..., "arhodes19044" <spamiam@c...> wrote:
> Is there an external timer commercially available and relatively
> inexpensive that is easy to interface to a BX-24?
>
> I am hoping to find something accurate to a few seconds a year and
> with better granularity than 1/512 of a second. Temperature
> compensation would be a great thing as well. Lithium watch battery
> backup would be great too!
>
> Any ideas of what to use?

The DS2404 may fit the bill. As a bonus, it has a 1Hz square wave
output signal. You can interface it to the BX-24 using either the
1-wire or 3-wire interface. I have experimented with it a little
using the 1-wire interface. It's fairly easy to use.

Don



Yeah, I guess it is overkill. I just was thinking about my
wristwatch. It seems good to a few seconds per year. I check it
against NIST periodically and it is just about dead on. (Seiko Kinetic)

So, I figured that if a quartz watch can deliver this accuracy, then
some specialized chip should do the same.

Actually all I need is quartz accuracy. I just would not want more
than a second per DAY. Some rallies span a few days, but there is the
opportunity to re-synch every day, but maybe not more often than
that. For the really good ralliests, one second inaccuracy is the
difference between a win and a loss. So, with that in mind, I would
rather have accuracy to maybe 1/4 second per day, or 7 seconds per
month, or 90 seconds per year....

The chip that Don suggested is only good to +/- 120 seconds per
month. Not good enough.

DO you have any idea of the accuracy of the BX's clock? I can check
it myself, and will, but I was wondering if someone has come up with
the min/max data.

I have considered a GPS time base, but that is getting ahead of
everyting. Remember this is just a practical exercise.

BTW, it sounds as if you are familiar with Road Rallies. Do you have
experience with them? I find them rewarding as a driver and
frustrating as a navigator. I find a rally computer as much of a
liability as a benefit (GIGO, and I am full of garbage!)
-Tony
--- In basicx@basi..., "Tom Becker" <gtbecker@r...> wrote:
> > ... accurate to a few seconds a year...
>
> Not likely unless you use an atomic source. If you need long-term
> accuracy, use GPS or get your own Cesium oscillator. For a rally
> computer, that's extreme overkill. > Tom >
> Tom Becker
> --... ...--
> GTBecker@R... www.RighTime.com
> The RighTime Clock Company, Inc., Cape Coral, Florida USA
> +1239 540 5700



As an ex-Pro Rally driver and a current professional rally instructor,
you're more right than you might imagine. Accuracy is needed only for the
stage that is being run by each car or, put another way, you would need
accuracy that is a fraction of a second for the time that it takes to car
to run a stage which is rarely more than 30 minutes and is often less than
10 minutes. Note that the World Rally Championship only scores to tenths of
a second.

To paraphrase David Hobbs, the road racer, the driver usually runs out of
talent long before he runs out of pavement (or timing accuracy) <gg>.

Paul

At 02:15 PM 4/1/2005, you wrote: > > ... accurate to a few seconds a year...
>
>Not likely unless you use an atomic source. If you need long-term
>accuracy, use GPS or get your own Cesium oscillator. For a rally
>computer, that's extreme overkill. >Tom >
>Tom Becker
>--... ...--
>GTBecker@GTBe... www.RighTime.com
>The RighTime Clock Company, Inc., Cape Coral, Florida USA
>+1239 540 5700 >
>
>Yahoo! Groups Links >
>

===========================================================
"We have the power to do any damn fool thing we want to do,
and we seem to do it about every ten minutes."
J. William Fulbright , quoted in Time (New York, Feb. 4, 1952).
===========================================================



> ... I would rather have accuracy to maybe 1/4 second per day, or 7
seconds per month, or 90 seconds per year...

Assuming these are equivalent ratios, they do not put the same demand on
a timekeeping device, oddly. A clock that satisfies the short-term
accuracy spec might not be able to achieve either of the longer-terms,
and vice versa; a Hydrogen maser clock, for example, is not particularly
good at short period measurements but it is exceedingly good when
averaged over a longer period.

> ... Do you have any idea of the accuracy of the BX's clock?

Isn't that where you started with the BX-24 interrupt thread? It's
about the same as a watch - if it is continuously powered and reasonably
temperature stable; 10-30ppm. You can make it a good bit better with
temperature elevation and software correction, but it isn't a trivial
task.

If your Seiko Kinetic can keep two seconds per year it is an
exceptionally stable and very uncommon wristwatch. Tom
Tom Becker
--... ...--
GTBecker@GTBe... www.RighTime.com
The RighTime Clock Company, Inc., Cape Coral, Florida USA
+1239 540 5700


DS1302 arhodes19044 wrote:

>
> Is there an external timer commercially available and relatively
> inexpensive that is easy to interface to a BX-24?
>
> I am hoping to find something accurate to a few seconds a year and
> with better granularity than 1/512 of a second. Temperature
> compensation would be a great thing as well. Lithium watch battery
> backup would be great too!
>
> Any ideas of what to use?
>
> -Tony > *>.




Tom is right in both respects. I have a particular interest in "time"
and in my office I have 4 old electro-mechanical pendulum master clocks.
A Gents, an IBM, an TMC and a Burk. By dudicious adjustment of the
pendulum length nuts, I can get accuracy of about 2 seconds a month.
I use an atomic clock on the internet to check the time, in conjunction
with a very useful program called Chamelion. Chamelion interogates
atomic clocks and will correct your computer clock to within 1msec. It
is much better than Atomic.exe, which is not much use. I also have a
DS1302 RTC clock chip running 24/7 on my bench and it drives a Gents
slave clock face, which is advanced every 30 seconds. It is also
accurate to within 1 sec per week but it is badly temperature dependant
due to the Xtal and the Xtals caps temperatue coef. It also took me
about a month to get it to this degree of accuracy becuase when your
clock is getting to better than a second every day or two, it takes
several days to make an adjustment. I also have a DS1302 driving a tower
clock in the local town square, and it gains 5sec a month, which means I
need to adjust it about once a year. The BX24 clock is also pretty
good, if you take the time to run it continuously. It has the advantage
that you can do software corrections once you have established the error
rate. Recently I randomly chose a BX24 out of a box of 50 and it ran
better than a second a day without any correction. Its the checking that
takes the time.
My computer clock on the other hand is terrible. It runs within a few
msec an hour when the power is on, but overnight, when the power is off,
it loses 3 seconds in 12 hr. However Chamelion takes care of that. My
wrist watch loses 1 sec a month if I don't take it off. A wrist watch
has a built-in temperature regulator. However if I leave it on the bench
for a month it gets worse. Your watch as Tom says, is exceptional.

neil

Tom Becker wrote:

> > ... I would rather have accuracy to maybe 1/4 second per day, or 7
> seconds per month, or 90 seconds per year...
>
> Assuming these are equivalent ratios, they do not put the same demand on
> a timekeeping device, oddly. A clock that satisfies the short-term
> accuracy spec might not be able to achieve either of the longer-terms,
> and vice versa; a Hydrogen maser clock, for example, is not particularly
> good at short period measurements but it is exceedingly good when
> averaged over a longer period.
>
> > ... Do you have any idea of the accuracy of the BX's clock?
>
> Isn't that where you started with the BX-24 interrupt thread? It's
> about the same as a watch - if it is continuously powered and reasonably
> temperature stable; 10-30ppm. You can make it a good bit better with
> temperature elevation and software correction, but it isn't a trivial
> task.
>
> If your Seiko Kinetic can keep two seconds per year it is an
> exceptionally stable and very uncommon wristwatch. > Tom >
> Tom Becker
> --... ...--
> GTBecker@GTBe... www.RighTime.com
> The RighTime Clock Company, Inc., Cape Coral, Florida USA
> +1239 540 5700 >
> *>.





That is a really nice device. It has some really good day/date and
interval functions.

Its granularity is 1/256 second, not better than the BX-24 itself.
I can not tell about the temperature compensation. I would assume
that it is at least as good as the BX-24's. It uses an external
oscillator. and the connections are noise sensitive. It may be
sufficiently sensitive that it is not applicable to my uses.

You are right, the 1hz signal is perfect for me too!!!!

I may try one of these out. They are not "cheap", though.

Great device, and thanks for the heads up on this one!

-Tony

--- In basicx@basi..., "Don Kinzer" <dkinzer@e...> wrote:
>
> --- In basicx@basi..., "arhodes19044" <spamiam@c...> wrote:
> > Is there an external timer commercially available and relatively
> > inexpensive that is easy to interface to a BX-24?
> >
> > I am hoping to find something accurate to a few seconds a year
and
> > with better granularity than 1/512 of a second. Temperature
> > compensation would be a great thing as well. Lithium watch
battery
> > backup would be great too!
> >
> > Any ideas of what to use?
>
> The DS2404 may fit the bill. As a bonus, it has a 1Hz square wave
> output signal. You can interface it to the BX-24 using either the
> 1-wire or 3-wire interface. I have experimented with it a little
> using the 1-wire interface. It's fairly easy to use.
>
> Don



> ... accurate to a few seconds a year...

Not likely unless you use an atomic source. If you need long-term
accuracy, use GPS or get your own Cesium oscillator. For a rally
computer, that's extreme overkill. Tom
Tom Becker
--... ...--
GTBecker@GTBe... www.RighTime.com
The RighTime Clock Company, Inc., Cape Coral, Florida USA
+1239 540 5700



Hello, Paul.

Yes, I am into Pro Rally, but as a support person. My brother is a
navigator for the RedMist Rally team. "Our" vintage Datsun 510 is
due to be back on the road this summer, but probably not ready for
Wellsboro. We had a minor setback when our former car met a tree.
Missed a shift on a tight corner... unable to power thru the
pendulum, and physics took over.

I do drive and navigate for Road rally. In this case we may go all
day without time checks. Even here a fraction of a second (in being
on time) may be that fraction that takes you over the one second
margin and a loss could occur. In my own case, rarely am I at the
+/- 1 second range!!!! HAHAHA!

-Tony --- In basicx@basi..., Paul Dubinsky <pdubinsky@f...> wrote:
> As an ex-Pro Rally driver and a current professional rally
instructor,
> you're more right than you might imagine. Accuracy is needed only
for the
> stage that is being run by each car or, put another way, you would
need
> accuracy that is a fraction of a second for the time that it takes
to car
> to run a stage which is rarely more than 30 minutes and is often
less than
> 10 minutes. Note that the World Rally Championship only scores to
tenths of
> a second.
>
> To paraphrase David Hobbs, the road racer, the driver usually runs
out of
> talent long before he runs out of pavement (or timing accuracy)
<gg>.
>
> Paul
>
> At 02:15 PM 4/1/2005, you wrote: > > > ... accurate to a few seconds a year...
> >
> >Not likely unless you use an atomic source. If you need long-term
> >accuracy, use GPS or get your own Cesium oscillator. For a rally
> >computer, that's extreme overkill.
> >
> >
> >Tom
> >
> >
> >
> >Tom Becker
> >--... ...--
> >GTBecker@R... www.RighTime.com
> >The RighTime Clock Company, Inc., Cape Coral, Florida USA
> >+1239 540 5700
> >
> >
> >
> >
> >Yahoo! Groups Links
> >
> >
> >
> >
>
> ===========================================================
> "We have the power to do any damn fool thing we want to do,
> and we seem to do it about every ten minutes."
> J. William Fulbright , quoted in Time (New York, Feb. 4,
1952).
> ===========================================================